Match the following : Column-  I (Compound )  Column - II ( Valency of central atom )

In  ${\text{CO}}_2$, valency of Carbon is 4. This is because in  ${\text{CO}}_2$ Carbon forms four bonds with two Oxygen atoms.

In CO, valency of Carbon is 2. In CO molecule, Carbon forms two bonds with a single Oxygen atom. The remaining two electrons as lone pair at C atom.

In ${\text{NH}}_3$ , valency of Nitrogen is 3. To get octet Nitrogen combines with 3 H atoms. In HCl, valency of hydrogen is 1 . Both H and Cl are mono valent elements.